1. Field of the Invention
The present invention relates to a headgear assembly for use in holding a patient interface such as a respiratory mask in position on a patient's face, the patient interface being used in the treatment, e.g., of Sleep Disordered Breathing (SDB) with Non-Invasive Positive Pressure Ventilation (NIPPV).
2. Description of Related Art
Respiratory mask assemblies for treatment of SDB such as Obstructive Sleep Apnea (OSA) are typically secured to the patient's head by means of a headgear assembly.
Headgear assemblies are structured to position and stabilize a patient interface, such as a nasal mask, on a patient's face so that a good seal can be maintained. A headgear assembly typically includes a pair of side portions, and a rear portion. The side portions are adapted to engage with the patient's mask, and the rear portion is adapted to engage the back of the patient's head.
Prior art headgear arrangements typically have side straps typically held in position using hook and loop material, for example VELCRO®, by passing an end of the strap through a loop on the mask—or on a connector which connects to the mask—and then folding it back onto itself. In this way, the strap can be adjusted to adjust the headgear tension and thus the force which the headgear applies to hold the mask against the patient's face, to suit the particular needs of the patient in order that a comfortable effective mask seal be effected.
Correct adjustment of the headgear tension is important to the success of the therapies and to achieving patient compliance with the therapy regime.
Currently, patients generally use mask comfort to determine the headgear tension adjustment. However, the time period over which the patient is adjusting the tension is short in comparison with the length of each therapy session, and what feels comfortable over a 5 or 10 minute adjustment period will often be too tight to maintain comfort over an 8 hour therapy session. Also, changes in treatment pressure at the mask may require different headgear tension settings for optimal performance.
The ideal headgear tension is the loosest possible to maintain a seal between the mask cushion and the patient's face. However, it is intuitive for the patient to continue to tighten the headgear straps to seek to eliminate mask leak completely. In some instances, overtightening of the headgear may crush the sealing cushion of the mask and in fact increase the leak.
Furthermore, overtightening may cause patient discomfort, marking or creasing of the patient's face and neck which is visible the next day, and may lead to sores and tissue necrosis. Other possible effects of overtightening include dental and gum impairment, and pressure on the temporomandibular joints causing headaches, increased occurrence of apnea, or a reduction of nasal passage area leading to increased breathing resistance. All of these may make the therapy unpleasant for the patient and may lead to non-compliance with the therapy by the patient.
Alternatively, insufficient headgear tension may lead to mask leak by failure to maintain a seal between the mask and the patient's face, or movement of the mask while the patient sleeps, which may limit the success of the therapy or may wake the patient and lead to the patient discontinuing the therapy.